They argue that "traditional" plant breeding techniques cannot possibly provide the increase in yields that will be necessary to feed everyone.

With up to 40% of the world's food production lost to weed growth, pests and diseases, and with increasing desertification and urbanisation diminishing the amount of available agricultural land, the companies believe the demand for their technology will become irresistible.

Tony Coombes, from the biotech company Monsanto, accused Christian Aid of getting the facts wrong. He says the terminator technology does not, as yet, even exist. Although Monsanto has patents on it, he says such technology is at least five years away from possible commercialisation.

"Nobody is forcing farmers to do anything," he adds. "If they want to carry on saving their seeds and using them in future seasons, then that is fine."

Professor Don Grierson, who has developed GM tomatoes at Nottingham University, says Christian Aid has failed to find out about some of the benefits of the new technology, "such as insect and virus resistance, improved nutrition and reduced post-harvest spoilage.

"There is no spraying involved, the seeds inherit the change and this technology can be given to people in developing countries," he says.